The spring that was originally attached was too weak, so I was looking for reinforced goods. I tried to go around the shops in my neighborhood and purchased a powerful one, but because it was a tough place in terms of dimensions, the thick wire diameter got in the way and got in close contact and failed. Moreover, even if it is incorporated near close contact, is it a spring that can be used tightly? There is no data on what kind of spring it is. It was a difficult place to exchange next time if I got organized once, and I was worried about hesitancy. Finally we searched on the internet and reached the spring and it was powerful, and it also stated about the dimensions and the amount of deflection that can be used, so we did not hesitate to purchase and we were able to replace it with a powerful spring. It will be a long time before the result comes out, including durability, but I think that we can not think any more.